This invention relates to a print cartridge for an image forming apparatus, such as an electrophotographic copying machine and a printer, by which a cartridge, an image carrying body, a primary static charger and a cleaner can be integrally withdrawn from and inserted into a body of the apparatus.
In a known image forming apparatus, image forming devices, such as a primary static charger, an image exposing portion, a developing device, a transfer static charger and a cleaner, are arranged around the periphery of an image carrying body. After the surface of the image carrying body is uniformly and electrostatically charged by the primary static charger, the image is exposed to form an electrostatic latent image, and this electrostatic latent image is developed by the developing device into a visible image. This visible image is transferred to paper by the transfer static charger. The paper is fed to a fixing device for fixing purposes, and the residual toner on the image carrying body is cleaned off by the cleaner.
In such an image forming apparatus, the lifetime of the image carrying body as well as the lifetime of the image forming devices are short, and they need to be periodically inspected, repaired and exchanged. For example, as disclosed in Japanese Laid-Open (Kokai) Patent Application No. 65049/87, an image carrying body and some of image forming devices are integrally formed into a print cartridge, and the print cartridge is removably attached to the body of the apparatus, thereby facilitating a maintenance such as inspection, repair and exchange operations.
In the above-mentioned print cartridge of the type in which the image carrying body and the primary static charger are integrally formed into the print cartridge, in the case where high voltage is applied to the primary static charger, or in the case of corotron where the primary static charger has a grid, in order to reduce the electric field strength E (KV/cm) to prevent leakage, it has been recently common practice to electrically connect the grid and a shield electrode of the primary static charger to keep them at the same electric potential. It is also common practice to apply a bias thereafter so that the grid and the shield (serving as the shield electrode of the primary static charger) can be at the same electric potential. Therefore, it is necessary to apply the bias to the shield and the grid from the apparatus body, and besides, the primary static charger and the grid need to be removably attached to the apparatus body. Therefore, these are very cumbersome and difficult.